In the past, cam locks have been installed in file cabinets and other metal cabinets from the front. A spring retaining clip carried by the lock had two spring ears flaring outwardly toward the panel. The lock would be pressed through an opening in the drawer panel, and after the lock was fully in position, with its face plate pressing against the outer surface of the panel, the ears snapped out, pressing against the inner surface of the panel to hold the lock in place.
If the lock was single cam, the cam could be pre-installed on the lock and slipped through the hole at the same time. If two cams were required, one cam for each of two drawers, an L-shaped piece (two perpendicular cams) was used. This piece could not fit through the panel opening and, so, would have to be attached from the rear with a Keps nut (combined nut and lock-washer) or a Sems screw after the lock was in place. This meant that the lock could not be fully pre-assembled. This system, then, required considerable work behind the panel, was relatively expensive, and often resulted in cut fingers, in addition to low employee morale. Since cost of manufacture is critical when one is making low-end file cabinets, the ability to pre-assemble a lock, including its cams, becomes important.